Methods Debuts EDM Innovations from Fanuc at Metal Storm

[Editor's Note: This is continuing coverage of the recent Metal Storm machining technology event, of which ThomasNet News was invited to attend.]
Fanuc's RoboCut electric discharge machining (EDM) systems and controls were among the draws at Metal Storm, a biennial equipment and technology open house presented earlier this month by Methods Machine Tools in Sudbury, Mass. One machine on display was a new RoboCut with a 31iB series control offering an innovative capability: volumetric automatic taper compensation of the wire, or TPCMP.
What TPCMP means, says William Burba, an applications engineer at Methods, is that a RoboCut machine maintains a consistent burn rate as the wire moves through a cut. In EDM systems the speed of a wire deviates with the shape of a cut and creates overburns or underburns on the top and bottom of a part.

Fanuc developed an "e-value," which is calculated from a part's relevant dimensions -- width, height, and taper. The e-value is plugged into the 31iB CNC, and the control manipulates four axes of wire travel -- X, Y, U, and V -- along with distance to maintain a consistent burn rate.
With the e-value, the 31iB control reportedly achieves machining accuracy of 2 microns (0.00008 in). The control is available on Fanuc's c400iA and c600iA RoboCut machines.
The control and a c600iA machine were among the EDM units, precision machining systems, advanced automation systems, and components on display at Metal Storm. All told, more than 50 machines were under power, including machining centers, advanced automation systems, and metrology devices.
Among other Fanuc RoboCut innovations shown was Pulse Mode 91, which permits the machining of graphite ribs or walls as thin as 0.013 in (0.33 mm) from blocks up to 8 in thick. John Moldenhauer, EDM applications manager, says the capability significantly raises thinwall machining performance that can be reliably achieved with graphite. Typically, the material is too brittle to accurately cut sections this thin.
"A lot of companies face these challenges and will benefit from this new graphite cutting technology," Moldenhauer remarked.
The key is the pulse that minimizes the potential of graphite to fracture during machining, according to the company. As a result, sections that are almost one-third thinner than usual can be machined. The feature is available on current RoboCut ciA Series EDM units.
Just before the open house, Methods added a new single-axis EDM rotary table from Fanuc to the lineup it carries. Moldenhauer says the CCR table is designed and manufactured by Fanuc solely for the RoboCut EDM machines. As a result, it costs up to 50 percent less than a table from a third-party supplier and has "far more functionality built in," he added.
The CCR table is equipped with a sensor that triggers a servo motor and an encoder alarm if a seal ruptures and water gets into the compartment where both are located, shutting down the machine and draining the water tank. This minimizes the potential for expensive water-related repairs to the motor and encoder.
Moldenhauer notes that more of Methods' EDM customers have been adding rotary tables because the range of motion they provide increases opportunities for work in high-tech markets such as aerospace and medical.
Rotary tables also have an economic impact on the manufacture of cutting tools, especially when paired with the relatively high production speeds of some Fanuc EDM machines. One example Moldenhauer cites is rotary PCD (polycrystalline diamond)-tipped tool bodies.
The bodies can be fabricated by EDM or by grinding. (PCD tips are braised to the bodies in a secondary process.) The speed of recent EDM models and the use of rotary tables allow operators to produce these components rapidly, accurately, and at lower cost than with a diamond grinder, Moldenhauer says.

The CCR rotary table measures 6.1 by 6.5 by 5.1 in, weighs 33 lb, and takes a maximum load of 88 lb. Its indexing accuracy is 3.6 s, and its repetitive accuracy is +/- 0.2 s.
Another RoboCut development on display was Taper AWR, which automatically repairs a broken wire at the point of the break, even if it happens on a taper. Moldenhauer says Taper AWR has a control that calculates where the thread groove is and centers the head over it for wire repair. As a result, operators do not have to return to the starting point of a cut if a wire breaks.
The two-day Metal Storm open house, June 11-12, attracted more than 1,400 registered attendees from across the country. The equipment on display and the co-located seminars "represent new technologies and new ways to approach manufacturing a part," said Bryon Deysher, president and CEO of Methods. Attendees for the most part were looking for "automation and new ways to cut production costs," he added.
The open house was "somewhat of a dress rehearsal for IMTS" in September, he acknowledged, referring to the International Manufacturing Technology Show in Chicago. But it was also "a technology-in-action event," and with the first quarter "a bit slow" for the industry, Deysher was looking for Metal Storm to put companies in a buying mood.
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